CVE-2018-10903: Cryptography PyCA Cryptography Vulnerable To GCM Vulnerability

HIGH
Advisory Identifier: GHSA-fcf9-3qw3-gxmj
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CVSS 7.5
CWE-20
Published
Advisory Summary

CVE-2018-10903 is a HIGH (CVSS 7.5) pyca cryptography vulnerable to gcm vulnerability (CWE-20: Improper Input Validation) affecting Cryptography libraries in the PyPI ecosystem. The issue involves pyca cryptography vulnerable to gcm tag forgery. Remediation is available by upgrading affected packages to version 2.3.

CVE-2018-10903 at a Glance

CVE Identifier CVE-2018-10903
GHSA Identifier GHSA-fcf9-3qw3-gxmj
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-20: Improper Input Validation
Affected Product Cryptography
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2018-10903

To remediate this vulnerability, upgrade all affected Cryptography dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

cryptography fixed: 2.3 
pip install cryptography>=2.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show cryptography

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2018-10903, inspect your installed packages using pip:

pip show cryptography

Analyze the terminal output to locate any version of Cryptography in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.3), your application is affected.

Note: The pip show cryptography command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Cryptography, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalize_with_tag an attacker could craft an invalid payload with a shortened tag (e.g. 1 byte) such that they would have a 1 in 256 chance of passing the MAC check. GCM tag forgeries can cause key leakage.

CVE-2018-10903 Affected Cryptography Versions

1 component(s)
Fixed Versions:
2.3
Product / Package Ecosystem Affected Versions Fixed Version
cryptography
pypi/cryptography
PyPI
≥ 1.9.0
< 2.3
2.3

References

NVD — CVE-2018-10903 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-10903
Cryptography Source Repository REPOSITORY
https://github.com/pyca/cryptography/pull/4342
Security Fix Commit FIX COMMIT
https://github.com/pyca/cryptography/commit/d4378e42937b56f473ddade2667f919ce32208cb
access.redhat.com/errata/rhsa-2018:36... WEB
https://access.redhat.com/errata/RHSA-2018:3600
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-10903
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-fcf9-3qw3-gxmj
Cryptography Source Repository REPOSITORY
https://github.com/pyca/cryptography
Cryptography Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2018-52.yaml
usn.ubuntu.com/3720-1 WEB
https://usn.ubuntu.com/3720-1

Frequently Asked Questions

What is CVE-2018-10903?
CVE-2018-10903 is a security vulnerability in Cryptography involving PyCA Cryptography vulnerable to GCM tag forgery under CWE-20: Improper Input Validation.
Which Cryptography versions are affected?
Affected versions include releases prior to 2.3 across affected packages: cryptography.
What version fixes CVE-2018-10903?
Upgrading to 2.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is cryptography affected?
Yes, cryptography is affected in releases prior to 2.3. Upgrade your dependency to 2.3 or later.
What is the CVSS score of CVE-2018-10903?
CVE-2018-10903 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2018-10903?
CVE-2018-10903 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check PyPI dependencies for CVE-2018-10903?
Run the dependency tree command: 'pip show cryptography'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-fcf9-3qw3-gxmj",
  "modified" : "2024-09-13T18:13:03Z",
  "published" : "2018-07-31T18:28:09Z",
  "aliases" : [ "CVE-2018-10903" ],
  "summary" : "PyCA Cryptography vulnerable to GCM tag forgery",
  "details" : "A flaw was found in python-cryptography versions between >=1.9.0 and <2.3. The finalize_with_tag API did not enforce a minimum tag length. If a user did not validate the input length prior to passing it to finalize_with_tag an attacker could craft an invalid payload with a shortened tag (e.g. 1 byte) such that they would have a 1 in 256 chance of passing the MAC check. GCM tag forgeries can cause key leakage.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "cryptography"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.9.0"
      }, {
        "fixed" : "2.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-10903"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pyca/cryptography/pull/4342"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pyca/cryptography/commit/d4378e42937b56f473ddade2667f919ce32208cb"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2018:3600"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-10903"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-fcf9-3qw3-gxmj"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pyca/cryptography"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2018-52.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://usn.ubuntu.com/3720-1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-06-16T21:34:18Z",
    "nvd_published_at" : null
  }
}